Arresting the surface oxidation kinetics of bilayer 1T′-MoTe2 by sulphur passivation

Abstract

MoTe2 garnered much attention among 2D materials due to stable polymorphs with distinctive structural and electronic properties. Among the polymorphs, 1T′-MoTe2 in bulk form is type—II Weyl semimetal while, in monolayer form is a quantum spin Hall insulator. Thus, it is suitable for a wide variety of applications. Nevertheless, 1T′-MoTe2 degrades within a few hours when exposed to the atmosphere and causes hindrances in device fabrication. Here the degradation kinetics of CVD-synthesized 1T′-MoTe2 was investigated using Raman spectroscopy, XPS, and microscopic characterizations. The degradation rate of as-grown 1T′-MoTe2 obtained was 9.2 × 10−3 min−1. Further, we prevented the degradation of 1T′-MoTe2 by introducing a thin coating of S that encapsulates the flakes. 1T′-MoTe2 flakes showed stability for several days when covered using sulphur, indicating 25 times enhanced structural stability.